The Internet Protocol: IPV4 Packets
Understand the structure of IPv4 packets, including header fields like version, length, TTL, and protocol types. Learn how IPv4 manages forwarding loops and adapts to different data link layers through MTU variations.
The IPv4 packet format was defined in RFC 791. Apart from a few clarifications and some backward compatibility changes, the IPv4 packet format did not change significantly since the publication of RFC 791. All IPv4 packets use a 20-byte header as shown below. Some IPv4 packets contain an optional header extension that is described later.
IPv4 Packet Header
The IP version 4 header
Fields of The Header
The main fields of the IPv4 header are:
- A 4 bit version that indicates the version of IP used to build the header. Using a version field in the header allows the network layer protocol to evolve.
- A 4 bit